The present invention relates generally to medical devices and, more particularly, to medical devices configured for insertion into a lumen or cavity of a subject.
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Several types of thermal treatment systems are known for treating certain pathologic conditions of the body by heating or thermally ablating targeted tissue. These thermal treatment systems have used various heating sources to generate the heat necessary to treat or ablate the targeted tissue. For example, laser, microwave, and radio-frequency (RF) energy sources have been proposed to produce heat, which is then directed to the targeted tissue in or around a selected body cavity. Thermal treatment systems have been used to thermally ablate prostatic tissue, as well as tissue of different organs. The term xe2x80x9cthermal ablationxe2x80x9d refers to exposing targeted tissue to a temperature that is sufficient to kill the tissue.
One particularly successful thermal ablation system is designed to thermally ablate prostatic tissue by a thermocoagulation process. In males, the prostate gland can enlarge and the prostatic tissue can increase in density resulting, unfortunately, in the closing off of the urinary drainage path. This condition typically occurs in men as they age due to the physiological changes of the prostatic tissue (and bladder muscles) over time.
To enlarge the opening in the prostatic urethra (without requiring surgical incision and removal of tissue), a conventional thermal ablation system employs a closed loop liquid or water-induced thermotherapy (WIT) system which heats liquid, typically water, external to the body and then directs the circulating heated water into a treatment catheter, which is inserted through the penile meatus and held in position in the subject undergoing treatment to expose localized tissue to ablation temperatures. The treatment catheter typically includes an upper end portion, which, in operation, is anchored against the bladder neck, and an inflatable treatment segment that is held, relative to the anchored upper end portion, such that it resides along the desired treatment region of the prostate.
In operation, the treatment segment expands, in response to the captured circulating fluid traveling therethrough, to press against the targeted tissue in the prostate and to expose the tissue to increased temperatures associated with the circulating liquid, thereby thermally ablating the localized tissue at the treatment site. The circulating water is typically heated to a temperature of about 60-62xc2x0 C. and the targeted tissue is thermally treated for a period of about 45 minutes to locally kill the tissue proximate the urinary drainage passage in the prostate and thereby enlarge the urinary passage through the prostate.
Referring to FIG. 1, the anatomy of the male urethra 5, showing a thermal ablation treatment region 10 in the prostate 11, is illustrated. The thermal ablation treatment region 10 is indicated by the lined region in the prostate 11. For thermal ablation therapy, the treatment can be targeted to be carried out in a localized treatment region called the prostatic urethra 6, the treatment region 10 being generally described as the upper portion of the urethra from the prostate, which extends generally below the bladder neck 12a and above the verumontanum 11b of the subject. Alternatively, the treatment region 10 may include the bladder neck 12a or a portion of the bladder neck 12a itself.
FIG. 2A illustrates a treatment catheter 20 used in a WIT prostate treatment system identified as the Thermoflex(copyright) System available from ArgoMed Inc. of Cary, N.C. As shown, the treatment catheter 20 includes a bladder-anchoring balloon 22, a treatment balloon 23, and an elongated shaft 25. The catheter 20 is flexibly configured so as to be able to bend and flex to follow the shape of the lumen (even those with curvatures as shown in FIG. 2A) as it is introduced into the lumen until the distal portion of the catheter 20 reaches the desired treatment site. The catheter 20 is sized as an elongated tubular body with a relatively small cross-sectional area having a thin outer wall so as to be able to be inserted into and extend along a length of the desired lumen to reach the desired treatment site.
As shown in FIGS. 2B and 2C, the catheter 20 includes inlet and outlet fluid circulating paths 26i, 26o, respectively, as well as a urinary drainage channel 28 (which can also be used to deliver medicaments therethrough while the catheter 20 is in position in the subject). In operation, heated fluid or liquid, such as water or a water-based liquid, is heated external of the subject, directed into the catheter 20, and circulated in the enclosed fluid paths 26i, 26o in the catheter 20. The fluid is directed such that it travels through the catheter via the inlet path 26i to the treatment balloon 23 located proximate the desired treatment site and then back out of the treatment balloon 23 to the outlet path 26o, and then out of the subject. As shown in FIG. 2C, the circulating fluid is directed into the treatment balloon 23 which then expands in response to the quantity of fluid residing or traveling therein.
In operation, in order to anchor the catheter 20 in a desired position or location within the prostate 11 (after the catheter 20 is inserted into the prostate 11) through the urethra 5, the anchoring balloon 22 is inflated via a fluid (or other inflation media) introduced through the shaft 25 to the distal portion of the catheter 20 to cause the anchoring balloon 22 to take on an expanded configuration and reside against the bladder neck 12a of the subject (FIG. 1). Thus, when expanded, the anchoring balloon 22 is adapted to position the treatment balloon 23 in the prostate relative to the bladder 12. When deflated, the catheter 20, including the anchoring and treatment balloons 22, 23, can be removed from the urethra 5 of the subject.
For ease of insertion within and removal from a subject, it is desirable that catheters used for thermal ablation, particularly the anchoring and treatment balloons of such catheters, have a low, smooth, substantially constant profile during insertion and removal. Unfortunately, conventional anchoring and treatment balloons, when deflated, may not have a low profile and may have an irregular, non-smooth profile configuration. This may be particularly problematic in those balloons that are formed to take on a predetermined radial inflated shape, which they can retain even when asymmetrically compressed or pinched, in a manner that exposes a portion of the balloon to increased pressures. Exemplary anchoring and treatment balloons 22, 23 of a catheter 20 used for thermal ablation of prostatic tissue are illustrated in FIG. 3 in respective deflated configurations. The illustrated anchoring balloon 22 has plurality of xe2x80x9cwingsxe2x80x9d 30 when deflated so as to provide sufficient material that creates an effective anchoring structure when the anchoring balloon 22 is inflated.
Unfortunately, the wings 30 of the anchoring balloon 22 may cause discomfort and/or irritation to a subject when inserted through a lumen or other body cavity, such as the male urethra. In addition, the treatment balloon 23, when deflated, has a diameter that is larger than the catheter shaft 25. The size of the treatment balloon 23 may also cause discomfort and/or irritation to a subject when inserted through a lumen or other body cavity, such as the male urethra.
In view of the above discussion, catheters and stents that are configured for insertion into a body lumen, such as the male urethra, are provided with one or more inflatable balloons having at least one elastic sleeve configured to encase or overlie the balloon(s). The elastic sleeve is adapted to inflate in response to inflation of a respective underlying balloon, and to deflate in response to deflation of the respective balloon. When a balloon is in a deflated condition, a respective elastic sleeve exerts a circumferentially compressive force against the balloon to cause a smooth, reduced cross-sectional profile of the balloon along an axial extent thereof. This smooth, reduced cross-sectional profile may facilitate passage of the catheter and/or stent through a body lumen during both insertion and extraction of the catheter and/or stent. In certain embodiments of the present invention, an elastic sleeve is configured as a unitary sleeve that extends over a plurality of underlying inflatable balloons.
Elastic sleeves, according to embodiments of the present invention, can retain their elasticity even after exposure to elevated temperatures, such as incurred during thermal or thermal ablation treatments so as to be able to collapse the underlying balloon to a configuration which presents a reduced or low profile (against the primary body) at the end of the thermal treatment.
Elastic sleeves that surround treatment balloons are configured to facilitate the transfer of heat, such as from heated fluid or other heated media, to tissue adjacent the sleeve. In certain embodiments, heat is provided to the tissue at a treatment region by circulating heated fluid in a closed loop system that includes the catheter. The heated liquid is held captured within the catheter and is directed to the treatment balloon that is positioned at the target site, and thus, the heat is transferred to the treatment region. In certain embodiments, the elastic sleeve has a thermal resistance such that a temperature drop through the elastic sleeve is no greater than about 2.5% and/or no greater between about 0.5 degrees and about 1.5 degrees (0.5xc2x0-1.5xc2x0 C.) for a set temperature of about 60-62xc2x0 C. when measured ex vivo.
According to other embodiments of the present invention, a thin layer of a material may be disposed between a treatment (or tissue molding or otherwise configured) balloon and a respective elastic sleeve. The material can be selected to facilitate heat transfer from a respective treatment balloon to the surrounding elastic sleeve. The fluid is biocompatible and may be one or a combination of, a gelatinous material, a cream, a material which transforms at the treatment temperature to another state (such as from solid to a liquid or from a viscous material to solid or which coagulates when exposed to a certain temperature), or a liquid such as oil (such as mineral oil or a cooking oil), saline, granulated solid or particulate matter such as salt crystals, or other materials such as hydrogels. Preferably, the material and elastic sleeve, together, have a reduced thermal resistance such that a temperature drop through the fluid and elastic sleeve is no greater than between about 1.5 degrees and about 2 degrees (1.5xc2x0-2xc2x0), and more preferably no greater than about one degree, and still more preferably, no greater than about 0.5-0.8 degrees when measured ex vivo.
In certain embodiments, the sleeve is configured such that with the material held therein, the externalmost surface temperature is greater than for corresponding sleeveless catheter configurations when measured ex vivo for catheters configured to transmit elevated or heated therapeutic temperatures to a subject. That is, the temperature is greater on the external surface of the sleeve of the catheter compared to the external surface of the treatment balloon on a catheter without a sleeve. In certain embodiments, the fluid is a viscous or semi-viscous medicinal or lubricant and/or biocompatible cream or gel such as a hydrocortisone cream or petroleum jelly or a vaginal or other intra-anatomical lubricant such as KY(copyright) jelly or a mixture lubricant/topical or local anesthetic such as LIDOCAINE. In other embodiments, a solid or particulate matter can be combined with one or more of the above fluids or materials. The solid or particulate matter can be selected for its ability to absorb or accumulate and distribute the heat through the sleeve.
Catheters and stents according to embodiments of the present invention may be advantageous because insertion and extraction into and from body lumens and cavities of a subject may be performed easily and with less irritation and/or pain to the subject. The sleeve can extend over one or more of the balloons used to mold or position the stent or catheter in the body. The sleeve can be chemically or mechanically attached to the underlying body such as with adhesives, ultrasonic or chemical bonding, friction fit, tied with sutures or string, and the like.
Certain embodiments of the present invention are directed to methods for thermally treating a natural body lumen or cavity. The method includes: (a) circulating fluid heated to above about 40xc2x0 C. in a closed loop system that includes a catheter with a radially expandable treatment balloon and an overlying sleeve with a quantity of a selected material disposed therebetween; (b) concurrently expanding the treatment balloon and sleeve; (c) liquefying the selected material responsive to heat delivered from the heated fluid; and (d) directing heat to travel through the treatment balloon, liquefied material, and sleeve, responsive to the circulating and expanding steps so that, measured ex vivo, the temperature at the outer surface of the sleeve is above one degree less than the temperature at the outer surface of the treatment balloon on a corresponding sleeveless version of the catheter.
The present invention may find use for both veterinary and medical applications. The present invention may be advantageously employed for treatment of subjects, in particular human subjects. Subjects, according to the present invention, may be any animal subject, and are preferably mammalian subjects (e.g., humans, canines, felines, bovines, caprines, ovines, equines, rodents, porcines, and/or lagomorphs), and more preferably are human subjects. In addition, the medical devices can be used in different natural body lumens, including, but not limited to, the prostate, the cervix or uterus, veins and arteries, the sinus cavity, the throat or esophagus, the intestines, the colon, the rectum, and the like.